Zack Greinke can become a free agent after this season, and unless the Milwaukee Brewers can extend his contract in the next week or so, they will start trying to trade the 28-year-old.

As Fox Sports’ Ken Rosenthal reported this week, Milwaukee has not yet made a decision on what to do with Greinke. The San Francisco Giants gave righty Matt Cain a six-year, $127.5 million deal in April and Greinke will almost certainly want a deal similar to that. He will almost certainly be able to get that kind of contract on the open market.

Greinke is currently 9-2 with a 2.82 ERA and a 1.17 WHIP. He has started 16 games so far this season and has thrown 102 innings, allowing just 97 hits and 22 walks while striking out 102 batters. It is his second season with the Brewers after going 16-6 with a 3.83 ERA and 1.20 WHIP last year.

He is by far Milwaukee’s best pitcher, but the Brewers can’t afford to lose him this offseason with nothing but a draft pick or two in return. It’s a tough spot for the Brewers to be in and it’s getting close to decision time.

The New York Yankees, Boston Red Sox and Los Angeles Dodgers are all sure to pursue a trade for Greinke. But the contending team most in need of starting pitching is likely the Detroit Tigers, who don’t have much after Justin Verlander and Doug Fister.

The St. Louis Cardinals and Toronto Blue Jays are also likely to be in the mix for the 2009 American League Cy Young Award winner.